This description relates to electronic paper display devices, their operation and their method of manufacture.
Digital paper displays are being developed as next generation display devices, succeeding liquid crystal displays (LCD), plasma display panels (PDP), and electroluminescence devices. In particular, electronic or digital paper is a display device in which letters or images are displayed on a flexible substrate, such as thin plastic, in which several million beads are scattered in oil holes within the substrate. The electronic paper can be re-used several million times.
An electronic paper display device operates as a core of flexible display substrates. The electronic paper display operates in accordance with the principle of electrophoresis, e.g., where an electromagnetic field is applied to a conductive material having conductive corpuscles scattered between thin flexible substrates to impart motility to the corpuscles. The electromagnetic filed is applied to the conductive corpuscles, such as charged particles, that are scattered between thin flexible substrates and the direction in which the corpuscles are arranged is controlled by changing the polarity of the electromagnetic field to selectively display data.
In a conventional electronic paper display device that employs collision electrification, an insulating layer is typically formed between charged particles inserted inside display cells and electrodes. A driving voltage is applied to the electrodes to prevent the charged particles and the electrodes from being directly connected and to maintain the initial state, e.g., the initial charge, of the charged particles. The charged particles move toward the electrodes to which the driving voltage is applied and the position to which the charged particles move is maintained, e.g., unless an additional voltage is applied to obtain a memory effect.
The conventional insulating layer is formed of polyethylene, polystyrene, polycarbonate, polyester, polypropylene, and SiO2, which differs from the material of the external surfaces of the charged particles. Due to friction, which may be caused by particle collision between the charged particles and the insulating layer, the electric charge of the particles may significantly increase so that the memory effect exceeds the particle driving voltage or the electric charge of the particles may decrease so that the memory effect is not maintained, e.g., particle collision may alter the electric charge of the particles to an amount different than the particle driving voltage. Since the conventional insulating layer is provided between the charged particles and the electrodes, when the charged particles collide with the surfaces of barrier ribs, the material of the charged particles that becomes electrified may also change.